1. Field of the Invention
The present invention is directed generally to communication systems and, more particularly, to method an apparatus for delivery of isochronous datagram delivery in a contention-based data communication system.
2. Description of the Related Art
Packet data communication systems are well known in the art. An example of a packet-based communication system is the Internet. A data message is broken into multiple data packets and transmitted on the communication system along with delivery address data and packet numbering data. The multiple data packets, which may be referred to as datagrams, may be transmitted over one or more communication pathways to the destination indicated by the destination address associated with each datagram. The datagrams are reassembled and delivered to the destination address.
Certain applications, such as email, are generally not time-sensitive. These applications will tolerate high-latency. That is, delays in transmission of the individual datagrams does not adversely affect the overall quality of service (QoS).
Other applications, such as voice over Internet protocol (VoIP) or streaming media require low-latency. That is, such applications are sensitive to delays in transmission of individual packets and the overall QoS may be adversely affected by delays. Transmission of low-latency traffic, such as VoIP over a multiple-access media, such as Ethernet, involve prioritization of the traffic by the sending node prior to injection onto the multiple-access media. The concept is to place the VoIP traffic ahead of other traffic within the sending node. These techniques typically do not guarantee that high priority, low-latency traffic will successfully access the transmission channel.
In another example, Echelon has developed a predictive P-persistent carrier sense multiple access (CSMA) that achieves low-latency via an access priority scheme. Other examples have been proposed in the literature.
In a wireless network application, a separate radio frequency (RF) channel is often used to send VoIP data as a completely separate data link path. This approach essentially eliminates contention for the RF channel.
A common alternative method is to provide sufficient capacity overhead such that low-latency traffic can flow sufficiently quickly within the confines of the existing media access control (MAC) protocol. While such applications achieve the desired low-latency and QoS, the overall system architecture results in low efficiency with respect to overall channel utilization.
Therefore, it can be appreciated that there is a significant need for a system and method for delivery of low-latency data over a contention-based data link. The present invention provides this, and other advantages, as will be apparent from the following detailed description and accompanying figures.